The hands can be grasped, the waist can be straight.
On April 7, researchers from the Institute of Vertebrate Paleontology and Paleoanthropology of the Chinese Academy of Sciences (hereinafter referred to as the Institute of Paleospine) and the American Museum of Natural History discovered three columns from the Early Cretaceous Period (about 130-110 million years ago) Fossiomanus senensis and Jueconodon cheni were featured in Nature.
Ecological restoration of Chinese diggers and Chen's diggertodons (drawn by Zhao Chuang)
Evidence for the convergent evolution of mammals
Evidence for the convergent evolution of mammals These two new species of mammals come from the "world-class fossil reservoir"-the Jehol Biota in western Liaoning, China.
Prototype specimens of the Chinese Digger (left) and Chen's Digger (right) (provided by Mao Fangyuan)
"Chinese digger is a mammalian animal, but it is not a mammal in the traditional sense, but a mammal-like reptile that is closely related to it.
Mao Fangyuan, the first and co-corresponding author of the paper and an associate researcher at the Institute of Paleospine, told the China Science News that the Chen’s digger is a mammal, so from a phylogenetic point of view, the Chinese digger and the Chen’s digger Although beasts live in similar times, their kinship is far apart.
Mammal phylogenetic framework and differentiation time of main taxa (relaxation analysis of research team members)
"What's interesting is that their bone morphology is very similar.
From the morphological point of view, the limb bones of these two animals are thick and short, especially the forelimbs, the front paws appear wider, and the claws are long and strong.
Comparison of the teeth and limb bones of Chinese Digger and Chen’s Digger after high-precision (sub-micron level) CT processing (provided by Mao Fangyuan)
Researchers believe that these are common adaptive changes in the limb bones of excavating burrowing animals, and they are also one of the evidences for the convergent evolution of the two species.
"Chinese Diggers and Chen's Diggers represent the first known burrowing life types in their respective groups.
Why the spine of mammals is different
Why the spine of mammals is different In addition to the common point of burrowing, the Chinese digger and Chen's digger have one thing in common with the spine, that is, the increase in the number of sacral vertebrae.
Mao Fangyuan introduced that from the perspective of evolution and development, the changes in the mammalian spine are mainly reflected in the deformation and quantitative changes of the spine.
Deformation refers to the morphological and functional replacement of the spine in two adjacent regions.
Researchers found that the ratio of the number of cervical vertebrae to the number of sacral vertebrae (CP, cervical to presacral vertebrae) can be used to estimate the deformation and quantitative change of the spine in the fossil.
"The Chinese digger has the smallest CP value known to be a mammalian animal, but it has the largest number of sacral vertebrae, which means that the number of vertebral body segments and the deformation of the vertebral body of the Chinese digger occur at the same time.
This study found through comparison that the number and morphological changes of mammalian fossils have a similar range of changes to living mammals.
Comparison of the main ecological habits of mammals in the Mesozoic era and the schematic diagram of the evolutionary development mechanism under gene regulation (provided by Mao Fangyuan)
In addition, the researchers speculate that, from the perspective of biological evolution, the number and morphological changes of species' spine are also related to their ability to adapt to the environment.
For example, slow-moving species tend to have a significant increase in the number of spine, while cats and other species that require a large amount of back movement during fast running tend to stabilize the number of spine, because too many spine numbers are not conducive to fast running.
"The plasticity of the developmental mechanism and the pressure caused by the ecological environment together have played a key role in the evolution of the morphological diversity of the spine in mammals.
" Mao Fangyuan said, "but there are also some phenomena in the fossils that cannot be explained by developmental biology.
There are also some unknown gene expression regulation mechanisms that need to be continuously explored and resolved in the future.
"
She said that at this stage, the research still stays at the basic level such as reporting new specimens.
In the future, there is still a lot of room for research on the specific morphology of the two specimens, and more in-depth and detailed research can also be carried out with the help of more auxiliary methods such as biostatistics.
"We hope that more modern biological methods can be incorporated into paleontological research, and we also hope that the reproducibility of paleontological experiments will be higher in the future.
" Mao Fangyuan said.
(Source: China Science News, Zhang Sixuan and Hu Minqi)
Related paper information: org/10.
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